I'll answer what I know:
There are three large buttons on the right bottom corner. The one in the middle says "click to browse books by tags". It opens a panel on the left where you can browse, among other things, by tags, see how many titles you have per tag, see only titles with a specific tag, etc.
You can also see the tags and sort by them in the normal window view (it's title, author, size, ..., tags)
I think calibre only "sees" the information it currently holds. So as long as you have a book with the wrong publisher's name, it will be on the list.